I recently found further information explaining the mysteries of mashing. I had again become perplexed by why water from Burton-upon-Trent is ideal for brewing pale ales, and was looking for answers.
I understood why the high gypsum (calcium sulphate) content is good, as the calcium reacts with phosphates and polypeptides in the mash to liberate hydrogen ions and lower the pH. But what about the high carbonate content of Burton water? Carbonate has a buffering effect which will oppose the action of the calcium, and keep the pH too high, which can lead to poor extract and haze formation.
Delving deeper into this dilema I reached for Lloyd Hind's Brewing Science and Practice, as I'd left my copy of Cyrus Uprum's Brewing Compendium at home. Lloyd Hind is the best source I've found on Burton water as he details mineral content of water from several different Burton water sources. I though the answer may lie in comparing the different analyses. Maybe only some wells were good for brewing pale ales with, and they had water with lower carbonate content?
It turned out the solution was simpler. Lloyd Hind says of Burton water: "Waters of this character appear to be unsurpassed for pale ales and are
used without treatment of any sort, ...
... other than boiling for half an hour
or an hour previous to reducing to mashing temperature."
So the famous Burton brewing water was not used untreated! Boiling water may be the simplest of liquor treatments*, but a liquor treatment it is. Boiling hard water causes calcium carbonate to precipitate out of solution, which is how scale forms on a kettle. So it is Burton water, with the carbonate reduced, that is unsurpassed for pale ales.
*Actually in practice adding some acid is a lot bleedin' easier but you do need get the water analysed and calculate how much acid is needed to get rid of the carbonate.